Evaluation of 3D-CRT, IMRT and VMAT radiotherapy plans for left breast cancer based on clinical dosimetric study

This paper aims to compare dosimetric differences based on three types of radiotherapy plans for postoperative left breast cancer. In particular, based on a clinical dosimetric study, the three-dimensional conformal radiotherapy (3D-CRT), intensity- modulated radiation therapy (IMRT) and VMAT plans were implemented on 15 cases of postoperative patients with left breast cancer with prescription doses of 5000cGy.

Dose volume histogram (DVH) was used to analyze each evaluation index of clinical target volume (CTV) and organs at risk (OARs). Except for homogeneous index (HI), D₂, each CTV evaluation index of 3D-CRT plan was inferior to IMRT and VMAT plans (P<0.05). Compared with the VMAT plans, IMRT has a statistical significance only in D_mean, V₉₅ (P<0.05). On the contrary, D_mean pertaining to the VMAT plan is much closer to the prescription dose with a V₉₅ coverage rate as high as 97.44%. For the infected lung, V₅, V₁₀ of 3D-CRT were the lowest (P<0.05), while V₂₀, V₃₀ were the highest (P<0.05) among the three types of plans. Here, the V₅, V₁₀ of infected lung were slightly higher (P<0.05) for the VMAT and IMRT plans. Each evaluation index of the contralateral lung and heart in 3D-CRT was the lowest (P<0.05). D₁ of contralateral breast was lower in both IMRT and VMAT plans, which were 1770.89±121.16cGy and 1839.92±92.77cGy, respectively. While D₁ of the spinal cord in IMRT and VMAT plans was higher, which were 1990.12±61.52cGy and 1927.38±43.67cGy, respectively. When the radiation dose of 500-1500cGy was delivered to the normal tissues, 3D-CRT significantly shows the lowest volume, VMAT is relatively higher. Monitor Units (MU) and treatment time (T) of VMAT were the least, only 49.33% and 55.86% of those of IMRT.

The three types of plans can meet the clinical dosimetry demands of postoperative radiotherapy for left breast cancer. The target of IMRT and VMAT plans has a better conformity, and the VMAT plan takes the advantages of less MU and treatment time.